The present invention relates to an electrophoresis analysis apparatus and a sample vessel used therefor, and particularly to an electrophoresis analysis apparatus suitably used for a DNA sequencer (DNA base sequence analyzer) for analyzing biochemical samples such as a DNA (Deoxyribonucleic acid) using a plurality of capillaries or micropassages as migration separation media, and a sample vessel used therefor.
A DNA analysis technology based on electrophoresis, particularly, a DNA sequencer (DNA base sequence analyzer) has been widely available. With the increased need for analysis, the necessity of improving the analysis throughput has been increased. One method of increasing the analysis throughput is to integrate electrophoresis media.
A thin gel layer formed between two flat glass plates has been conventionally used as electrophoresis separation media. On the other hand, a multi-capillary method using a plurality of capillaries each having a fine inside diameter has been proposed, for example, in Nature, Vol. 361 (1993), Kanbara, PP. 565-566, the specifications of U.S. Pat. Nos. 5,277,780, 5,366,608, and 5,274,240, Japanese Patent Laid-open No. Hei 5-72177, and PCT international publication for patent application No. Hei 7-503322. Such a method makes it possible to increase the degree of integration by making use of the fine inside diameters of the capillaries and to simultaneously analyze a large number of samples. In this method, further, since the cross section of migration passages becomes smaller than that of the conventional flat glass plates, a current caused by electrophoresis becomes smaller to thereby suppress generation of a Joule heat. As a result, by applying a higher electrophoresis voltage, a sample can be migrated at a higher speed. Accordingly, a number of samples can be simultaneously separated and analyzed at a high speed.
As a second method, a multi-capillary method of making use of fine grooves formed in a surface portion of a glass plate as migration passages has been proposed, for example, in the specification of U.S. Pat. No. 5,192,412 and Japanese Patent Laid-open No. Hei 5-93711. Even in this method, a number of samples can be simultaneously separated and analyzed at a high speed.
In the above-described multi-capillary method, first ends of an electrode and a capillary are first inserted in a sample contained in a sample vessel, followed by applying a voltage across the capillary to electrically migrate the sample into the capillary; and then the first ends of the electrode and the capillary are inserted in a buffer solution in a buffer bath, followed by applying a voltage across the capillary to separate the sample by electrophoresis.
In the case where the number of samples to be simultaneously analyzed is several pieces, since the number of electrodes/capillaries is the same as that of the samples, it does not take as much labor to insert the electrodes and capillaries in sample vessels and a buffer bath.
However, in the case where several tens of samples are simultaneously analyzed to improve the analysis throughput, it is difficult to insert electrodes and capillaries in sample vessels and a buffer bath. To be more specific, the amount of a sample generally used for a DNA sequencer is merely 5 .mu.l because it is difficult to prepare a large amount of a sample and also a reagent to be used is expensive. In the case where the sample in an amount of 5 .mu.l is put in a sample vessel having an inner diameter of 2 mm, the liquid level becomes only about 1.5 mm. It is very difficult to individually insert several tens of electrodes and capillaries in the above small-sized sample vessels.